Generally, a network device sends downlink control information (DCI) to a terminal device, to trigger aperiodic channel state information (CSI) reporting and/or uplink data transmission performed by the terminal device. The DCI includes a parameter that indicates the terminal device to perform CSI reporting. CSI reported by the terminal device to the network device usually includes parameters such as a rank indication (RI), a precoding matrix indicator PMI), and a channel quality indication CQI).
A parameter used by the network device to indicate the terminal device to perform CSI reporting is a rank indication restriction (RI restriction). The RI restriction parameter is used to indicate, to the terminal device, PMIs and RIs corresponding to ranks that are allowed to be reported. Another parameter used by the network device to indicate the terminal device to perform CSI reporting is a CQI number or a CQI maximum number (Num_CQI/Max_Num_CQI). The Num_CQI/Max_Num_CQI parameter is used to indicate a number of CQIs or a maximum number of CQIs that are reported by the terminal device. There is an association relationship between the number of CQIs or the maximum number of CQIs reported by the terminal device and a number of RIs reported by the terminal device.
It is found by the inventor during creation of this application that, the RI restriction parameter indicated by the network device to the terminal device conflicts with the Num_CQI/Max_Num_CQI parameter in some cases, and then the terminal device cannot perform RI reporting.